Video: From Allergies to Deadly Disease, Feeling the Effects of Climate Change

A rare but deadly fungal disease once occurring only in tropical climates has recently led to several deaths in the Pacific Northwest. Some researchers believe that climate change may be to blame for the disease's emergence there.

When Trudy Rosler first got sick after a visit to Vancouver Island in British Columbia, doctors were stumped. Eventually they discovered that she had fungus growing in her brain stem—one that was previously only known to exist in the tropics. Researchers say that subtle changes in climate over the last 40 years may be the reason it's infecting people much farther north. Here in the US, the Centers for Disease Control and Prevention is already treating climate change as a serious health threat.

Need to Know's medical correspondent Dr. Emily Senay examines how a warming climate is already affecting our health, from making allergies worse to affecting the spread of infectious diseases and pushing the extremes of killer weather.